biochem question..just don't get it!! - drdido

[ArchivalUser]

Guys and gals.. There is a question I have here that I just don't get. For those that have Kaplan Biochem 06/07, this should be familiar:

Here we go:

James K. is a Huntinigton disease patient who has recently been instiutionalized and requires constant nursing care. His wife is unaffected, and they have a 38 yr old daughter, Delia, who has 4 children ranging from 8 to 15 yrs. Delia wishes to know whether she has in herited the dis-producing allele from her father. PCR amplification is carried out on the region containing the CAG repeat, shown below. Which of the following sets of primers would be used to amplify the CAG reapeat in the brackets ([CAG]n)?

GAG TCC CTC AAG TCC TTC [CAG]n CAA CAG CCG CCA CCG CCG (<--- these 2 sets of codons..please attach,in their exact order,to the right hand side of the CCA above..if they don't already appear there.)

choices:
A) CTCAGGGAGTTCAGGAAG and CGGCGGTGGCGGCTGTTG
B) CTTCCTGAACTCCCTGAG and CAACAGCCGCCACCGCCG
C) CTTCCTGAACTCCCTGAG and CGGCGGTGGCGGCTGTTG
D) GAGTCCCTCAAGTCCTTC and CGGCGGTGGCGGCTGTTG
E) GAGTCCCTCAAGTCCTTC and GTTGTCGGCGGTGGCGGC

If you know the answer...please clarify and explain bec. I am not given an explanation at all.
Thanks so much.

[ArchivalUser]

Anyone ?????????

[ArchivalUser]

i've seen that question answered on the forum before.. i'll try searching for it

[ArchivalUser]

D). 5'-GAGTCCCTCAAGTCCTTC is sense primer, whereas 5'-CGGCGGTGGCGGCTGTTG.
is antisense, complimentory to CAA CAG CCG CCA CCG CCG .

[ArchivalUser]

The coding strand is
5`GAG TCC CTC AAG TCC TTC [CAG]n CAA CAG CCG CCA CCG CCG 3`
The complementary template strand is
3` CTC AGG GAG TTC AGG AAG [GTC]n GTT GTC GGC GGT GGC GGC 5`


To synthesize more coding strand by PCR, we need to synthesize
1. Its complementary template strands-----> we need primer---> primer has the same sequence as the 5` flank of this strand----> 5` CGG CGG TGG CGG CTG TTG 3` (the actual written sequence of "3` GTT GTC GGC GGT GGC GGC 5`")
2. Using this complementary template strands we can synthesize actual coding strands----> we need primer here too----> This primer is again the 5` end of the coding strand.----------> 5`GAG TCC CTC AAG TCC TTC 3`

Primer is short strand of DNA that can help start DNA synthesis by DNA polymerase. The length of Primer here is before the actual CAG repeats.

[ArchivalUser]

thank you all for your replies. keshkala.. i appreciate your detailed explanation. thx again.